Thursday, August 6, 2015

Gili rays- a lot of confusion!

We're very lucky at Gili Lankanfushi in that we get to see a
lot of beautiful ray species around the island. They can be spotted frequently
from the pontoon boats or be seen dancing around in the light from our water
villas and- if you're really lucky, they will sometimes make an appearance
during a snorkel trip too.

Can you identify this guy?A Spotted Eagle ray sighted at night off the villa

Perhaps due to their size or their graceful nature, they are
always an exciting thing to spot wherever you are. We often get guests visiting
us at the desk and telling us about which ones they've sighted that day and we
love identifying which species it was from descriptions of colour, shape,
behaviour or blurry photos. At a fleeting glance or a flick of a tail they can
appear quite similar and we've noticed that there's a lot of confusion
surrounding which ray is which. So we've decided to try and clear up the
confusion a bit with a brief overview of our rays at Gili!

We can start with some background information on rays...

Rays are actually very closely related to sharks and both
are what we call 'cartilaginous fish' (yes they are fish!) in the Elasmobranch
taxonomic class. These Elasmobranchs are different from most fish you see on
the reefs, like the parrotfish, butterflyfish, triggerfish and so on, as these
are all 'bony fish' or class Osteichthyes (also sometimes called 'true fish').
As you can imagine, the main difference between cartilaginous fish and bony
fish is the composition of the skeleton but sharks, rays and other members of
the cartilaginous fish class also have other unique features such as rigid
dorsal fins, special placoid scales and no swim bladder.

The rays themselves can come in many different shapes and
sizes. So here's a quick run down on the main ones we see around Gili...

STINGRAYS

Stingrays are bottom dwellers and this is an obvious trait
that we can use to identify them. They will spend their time on the seabed
either feeding, lying stationary to conserve energy or gliding around very
close to the sandy bottom. Sometimes they will cover themselves in sand for
camouflage, with only their eyes and tail visible. It can be quite alarming
when what you thought was a dead palm frond turns out to be the tail of a large
stingray!

Most stingrays have barbed stingers, usually at the base of
their tail, which they will only use for self-defense. Stingrays are not
aggressive and do not sting without being provoked. The only time to be wary of
stingrays is when entering the water, it’s important to check before jumping in
so that you don’t land on one!

A variety of stingrays can be spotted commonly under the villas! Credit: Vaidas Kirsys

EAGLE RAYS

Eagle rays do not live on the sea bottom but instead will be
found swimming or gliding gracefully through the water. They have quite
distinctive 'duck-like' snouts at the front of their diamond shaped bodies and
can occasionally be seen burrowing their snouts into the sand looking for food.
Whereas most of the stingrays are pale and sandy coloured, the eagle rays are
much more obvious with their dark blue/black colouring and bright white
underside. These rays can have very long tails, up to 5 metres, and can swim
very rapidly. They do also have barbed tails, however they are much more likely
to use their speed to escape and rarely use them.

The most commonly sighted eagle ray species is the
White-spotted Eagle Ray (Aetobatus ocellatus), has a dark blue/black dorsal
side with distinctive white spots and a white underside. (Photograph from
animalspot.net)

A reef Manta Ray at Vavvaru Island. Credit: Gianluca Arlotti

MANTA RAYS

Manta rays have to be the most popular rays at the dive
centre, with lots of guests keen to learn about them or asking where they can
go to see them. Manta rays are in the same family as Eagle rays (Myliobatidae)
and they too will be seen gliding through the water rather than on the seabed.
These rays are much larger in size than stingrays and eagle rays, reaching up
to 4.5 metres diameter in the reef manta ray! It is possible to see these
majestic rays by snorkeling, but you must be extremely lucky to encounter one,
and almost always outside the lagoon, as they are not sighted around the
shallow waters of Gili Lankanfushi or near the villas. For the best chance to
see them, you have to visit special diving sites by SCUBA. They will often
visit specific reefs to be cleaned by small cleaner wrasse or be seen scooping
up the plankton soup with their specialized cephalic fins. Certain times of the
year yield better chances of seeing them at different sites around the atolls,
but for us, between May and October is best. During this period, it is also
possible to see the mantas in large numbers at a place called Hanifaru Bay in
Baa Atoll, where we have recently started running a trip. Although it's almost
3 hours away, the chance to see 100+ mantas in one aggregation is something
that will stay with you for a lifetime. Ask about it next time you visit!

MOBULA RAYS

Mobula rays are very similar in form to manta rays, they are
very closely related, both being in the Mobulidae family. Understandably they
are often mistaken for their manta cousins but they are a much smaller species
than mantas and also have certain morphological differences. Both manta and
mobula rays are filter feeders which sets them apart from the stingrays and
eagle rays that feed on small molluscs and crustaceans buried in the sand. They
are also completely harmless with no stinging barb at all.These rays can be
spotted in the shallow waters around Gili, but they are quite rare!

Three Short-fin Devil Rays (mobulas) gliding through the water . They will often be found in schools of between 3-20. Credit: Josie Chandler

GUITARFISH

Finally, this strange creature! Is it a shark? Is it a ray? Is it a plane? It is in fact... a ray! Also sometimes called 'shark rays', these guitarfish look like they are half of each, but a few characteristics like their ventrally located mouth and gills, classify them as rays in the Rajiformes order. This ray can reach up to 3 metres in length and has on occasion been spotted cruising by guest villas!

Hopefully now you can tell your mobulas from your guitarfish and your mantas from your stingrays. Remember to look out for body shape, colouration and general behaviour when you see them- happy spotting!